The Freeze and Helix are, in fact, the same effect. The only difference is the labeling. Our early prototypes are labeled "Freeze" while the production units are labeled "Helix."
DJM 900 NXS2 Helix Layering Samples
So it looks like there was a freeze effect on some djm nxs2 where the helix effect is now at. I have seen some videos and they both allowed to roll a sample and also both allowed to pitch change it. There is a video which showed how to layer samples on the freeze effect and not sure if helix allows this feature. If it happens to not allow this feature please add this feature in a update to the helix effect. This would give the nxs2 mixer an extremely useful effect. I can see many djs utilizing this feature including myself in many creative ways.